Crane construction

ABSTRACT

A crane having an extensible boom with a hydraulic cylinder for extending and retracting the boom and a hydraulic winch motor on a nonextensible portion of the boom controlling the paying-out and taking-in of cable which suspends a load block and hook from the outer end of the extensible boom portion. The boom extension cylinder and winch motor are series connected in the same hydraulic circuit in a manner so that line is automatically paid out simultaneously and coextensively with the extension of the boom and at least at the same rate, whereby drawing up of the load block against the boom is prevented.

United States Patent 3 ,371,799 3/1968 Brownell 212/59 3,458,053 7/1969 Reuter 212/46 FOREIGN PATENTS 1,009,780 6/ 1957 Germany 212/55 Primary Examiner-Harvey C. Hornsby Altomey-Buckhorn, Blore, Klarquist and Sparkman ABSTRACT: A crane having an extensible boom with a hydraulic cylinder for extending and retracting the boom and a hydraulic winch motor on a nonextensible portion of the boom controlling the paying-out and taking-in of cable which suspends a load block and hook from the outer end of the extensible boom portion. The boom extension cylinder and winch motor are series connected in the same hydraulic circuit in a manner so that line is automatically paid out simultaneously and coextensively with the extension of the boom and at least at the same rate, whereby drawing up of the load block against the boom is prevented.

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CRANE CONSTRUCTION BACKGROUND OF THE INVENTION 1. FIELD OF THE INVENTION The present invention relates to cranes having extensible booms with a load-handling means suspended from the outer end of the boom.

2. DESCRIPTION OF THE PRIOR ART In cranes having extensible booms, extension of the boom tends to draw up the cable-suspended load-attaching hook or block against the sheave carried by the outer end of the boom, and damage to the cable or other parts will result if boom extension continues after this occurs. This problem, referred to in the art as two-blocking is sought to be avoided in the prior art either by (l) mounting a cable payout and takeup cylinder having a limited cable storage capacity on the extensible portion of the boom, which presents cylinder mounting and hydraulic connection problems, or by (2) stopping boom extension or releasing cable whenever two-blocking occurs. The last-mentioned approach does not prevent two-blocking, but only its harmful after effects.

SUMMARY OF THE INVENTION In accordance with the present invention, two-blocking is prevented altogether by commencing and continuing the payout of line from its winch automatically throughout the period during which the boom is extended and at a rate sufficient to at least maintain the load hook or block at its initial distance from the end of the boom. In accordance with an illustrated embodiment of the invention, simultaneous and automatic line payout with boom extension is accomplished hydraulically by connecting a hydraulic winch motor in series with the boom extension cylinder, with the discharge side of one being connected to the intake side of the other.

Accordingly, primary objects of the invention are to provide, in a crane having an extensible boom:

1. means for paying-out the load-supporting line automatically upon extension of the boom and at a rate equal to or exceeding the rate of extension of the boom to ensure that the load block or hook suspended by the line will not BRIEF DESCRIPTION OF THEDRAWINGS The foregoing and other objects and advantages of the invention will become more apparent from the following detailed description which proceeds with reference to the accompanying drawings wherein:

FIG. 1 is a side elevational view, largely in section, showing somewhat schematically a crane with hydraulically extensible boom in accordance with the present invention;

FIG. 2 is a diagram of a hydraulic circuit embodying the invention for use in the crane of FIG. 1; and

FIGS. 3 and 4 are simplified diagrams of alternative hydraulic circuits in accordance with the invention.

DETAILED DESCRIPTION With reference to the drawings, a hydraulic crane 10 is shown in FIG. 1 having an extensible boom 12 including an extensible outer boom portion 14 which telescopes within a nonextensible inner boom portion 16. Inner boom portion 16 is pivoted at a connection 18 to a boom support member 20, which in turn may be mounted on a vehicle bed for mobility. A hydraulic cylinder 22 is connected to nonextensible boom portion 16 at 24 for swinging the boom in a vertical plane about the axis of connection 18. A first fluid motor means comprising a hydraulic winch motor 26 carried by the nonextensible boom portion 16 drives a winch drum 28, also carried by the nonextensible boom portion. Winch drum 28 stores line means or cable 30 which is trained about a sheave 32 mounted at the outer end of extensible boom portion 14 and thence about a pulley block 34 before being anchored at 36 to an underside of extensible boom portion 14. Pulley block 34 carries a load-attaching means in the form of a hook 38.

A second fluid motor means comprising a hydraulic cylinder 40 is housed within inner boom section 16 and is connected thereto at 41. Cylinder 40 also extends within the inner end of extensible boom section 14 and has its piston rod 42 connected at 44 to the extensible boom section for slidably extending and retracting such section within inner boom section 16.

Referring to FIG. 2, a suitable hydraulic circuit is shown for coordinating the operation of reversible winch motor 26 and double-acting boom extension cylinder 40. The circuit includes a pump 46, which is supplied with pressure fluid from reservoir 47 and delivers it to winch motor 26, boom extension cylinder 40 or both through appropriate fluid passage means. Pump 46 may be either of a fixed displacement or of a variable displacement type. A three-position winch control valve 48 enables operation of winch motor 26 independently of boom extension cylinder 40. A three-position boom control valve 50 controls the extension and retraction of boom cylinder 40 and, because of the disclosed hydraulic circuitry, also activates winch motor 26 in a manner to be described. Boom extension cylinder 40 is connected hydraulically in series with hydraulic winch motor 26 by interconnecting means comprising a fluid passage 52. Passage 52 connects the discharge side of cylinder 40 with the intake or pressure side of the winch motor or the discharge side of the winch motor with the intake or pressure side of the cylinder, depending on which direction pressure fluid is caused to flow through the circuit.

counterbalance valves 58 and 60 and their corresponding pilot lines 59, 61 and check valves 57, 62 are provided to ensure that upon paying-out of cable 30 or upon retracting the boom, there is sufficient back pressure to permit a controlled lowering of the cable and cylinder retraction.

A winch drum brake 64 is applied by a spring 66 acting against piston 68 within hydraulic cylinder 70 and through a linkage 71. To release the brake, pressure fluid is applied to the lower end of piston 68 through a fluid passage 72.

OPERATION Winch control valve 48 and boom control valve 50 are shown in their neutral positions. When it is desired to operate the winch without also operating the boom extension cylinder 40, control valve 50 is retained in its neutral position and control valve 48 is moved to either its left-hand or right-hand position.

When moved to its right-hand position, valve 48 admits pressure fluid through valve passage 48a to line 74, from whence the fluid passes through check valve 57 and line 76 to the side 77 of winch motor 26 for operating the motor in a direction to take in line, or hoist the load. Exhaust pressure fluid returns from the winch motor through line 52, line 78, line 80, valve passage 48b and line 82 to sump 47. At the same time, exhaust pressure fluid from the winch motor, althoughnot isolated from boom cylinder 40, is prevented from retracting the cylinder by the centered position of boom control valve 50. While winch motor 26 operates, pressure fluid acts through line 86 and brake line 72 to release brake 64 and permit the winch drum 28 to rotate.

To lower a load or let out line, winch control valve 48 is shifted to its left-hand position. Thereupon pressure fluid from pump 46 flows through valve passage 48c, line 80 and line 78 to line 52 and then to the opposite side 79 of winch motor 26 to operate the motor in a direction for paying-out line from winch drum 28 and thus lowering a load suspended from the line. Under these circumstances exhaust fluid from the winch motor returns to sump through line 76, line 88, counterbalance valve 58, line 74, valve passage 48d and line 82.

As evident from FIG. 2, to extend or retract the boom, winch control valve 48 must be centered in its neutral position to permit pressure fluid to pass from pump 46 through valve passage 48:: and line 90 to boom control valve 50. Thus such control valves and their circuits provide an interlock preventing independent operation of the winch during operation of the boom.

To extend the boom, boom control valve 50 is shifted to its left-hand position so that pressure fluid from line 90 passes through valve passage 52a to line 92 and then through line 84 into the lower end 85 of boom extension cylinder 40, extending the boom cylinder. As the boom cylinder extends, pressure fluid forced from the upper side 87 of the cylinder is discharged to line 52 which transmits the fluid pressure to side 79 of fluid motor 26, thus operating the winch motor in a direction for paying-out line from winch drum 28. At the same time, fluid pressure acting through line 78 and brake line 72 releases the winch drum brake 64 to permit the drum to spool out line. Shuttle valve 94 between lines 78, 86 and 72 prevents the return of pressure fluid to sump through lines 78 and 86 and boom control valve 50.

The volumetric fluid capacities of chamber 87 of cylinder 40 and winch motor 26 are correlated so that the rate of extension of cylinder 40 and the speed of motor 26 cause line to be paid out from winch drum 28 at least as fast as the boom extends. This interrelationship prevents block 34 from being drawn up against sheave 32 at the outer end of the boom upon extension of the boom. Preferably the volumetric capacities of the cylinder and motor are selected so that the line will pay out at substantially the same rate as the boom extends so that block 34 will remain at a preset constant distance from the outer end of the boom throughout any period of boom extension.

To retract the boom, boom control valve 50 is shifted to its extreme right-hand position so that pressure fluid acting through line 90 passes through valve passage 526 to line 86, to line 74, and through check valve 57 in line 76 to side 77 of winch motor 26 for operating the motor in a direction to take in line and hoist hook 38. Pressure fluid exhausted from side 79 of the winch motor passes to line 52 and into upper side 87 of boom extension cylinder 40, retracting such cylinder. Upon retraction of cylinder rod 42, fluid is exhausted from lower side 85 of such cylinder to line 96 and through counterbalance valve 60, which is opened by fluid pressure acting through pilot line 61, to line 92 and then through valve passage 52b and line 98 to sump.

If, previously suggested, the volumetric capacities of motor 26 and chamber 87 of cylinder 40 are correlated to pay out line and extend the boom at equal rates, the line will also be taken in at the same rate as the boom retracts to maintain a constant distance between pulley block 34 and the outer end of the boom during retraction. If, however, motor 26 pays out line faster than the boom extends to ensure that two-blocking does not occur during boom extension, there are circumstances where two-blocking could then occur upon boom retraction, since line would be taken in at a faster rate than the boom retracts. However, in the event two-blocking should occur upon boom retraction, line breakage is prevented by pressure relief valve 98 for pump 46. The relief pressure of such valve is set at a level less than that pressure which would be required to break the line, thus preventing winch motor 26 from developing enough power to break the line. Therefore, if two-blocking occurs on boom retraction, pressure relief valve 98 opens to return pressure fluid from the supply side of pump 46 back to sump, stopping the operation of winch motor 26 and boom extension cylinder 40.

It should be emphasized that the main problem in the past has always been in preventing two-blocking upon boom extension, and this is the primary problem to be solved by the present invention. The prevention of two-blocking upon retraction of the boom is really no problem as a practical matter, and can be prevented by pressure relief valve 98 or in other ways. For example, the hydraulic circuit of FIG. 2 might include the line 100 shown in dashed lines and including a check valve 102. Because of check valve 102, line 100 would not affect the operation of the circuit as described hereinbefore upon boom extension. However, upon retraction of the boom, line 100 would short circuit the winch motor 26 to prevent its operation altogether.

FIG. 2 illustrates a simple circuit for a two-stage crane boom operated by a single double-acting hydraulic cylinder. However, it is to be understood that the invention would also apply to a three-or-more stage boom operated by two or more hydraulic cylinders. Moreover, although a single reversible hydraulic winch motor is shown, two or more could be used. Furthermore, the circuit could be reversed so that pressure fluid is first directed to the side 79 of the winch motor for paying out line and then to the side 85 of the boom extension cylinder 40 for extending the cylinder. In any event, the fluid winch motor means and fluid boom extension motor means are series connected, with the discharge side of one such motor means being connected to the intake side of the other motor means to obtain the desired effect of simultaneous boom extension and payout of line.

FIG. 3 discloses a simplified hydraulic circuit incorporating a single-acting hydraulic boom cylinder 110, a reversible hydraulic winch motor 112, a fluid pump 114 for supplying pressure fluid to the winch motor and boom cylinder and a selector valve 116 for controlling the direction of flow of the pressure fluid. Boom cylinder has a piston rod 132 coupled by a rigid connection 122 to cylinder rod 124 of a second single-acting fluid cylinder 126, the pressure side 128 of which is connected in series with winch motor 112 by a line 130. Thus winch motor 112 defines a first reversible fluid motor means and the rigidly coupled single-acting cylinders 110 and 126 define a second reversible fluid motor means, which acting together accomplish the same purpose as the winch motor and double-acting cylinder 40 of FIG. 2.

To extend the crane boom in FIG. 3, valve 116 is shifted so that the pressure fluid is directed into line 118 and line 119 first to the winch motor 112 to rotate the winch drum in a direction for paying out line. Pressure fluid discharged from the winch motor then passes through line to the pressure side 128 of fluid cylinder 126, extending such cylinder. Because of the rigid connection 122 between cylinder 126 and cylinder 110, cylinder rod 132 of the latter cylinder extends, exhausting fluid from pressure side 134 of such cylinder through line 136 and valve 116 to sump 138.

To retract the boom in FIG. 3, valve 116 is shifted to direct pressure fluid from the pump and line 140 into line 136, from which the flow enters the pressure side 124 of boom extension cylinder 110, retracting such cylinder and thus the boom. Because of rigid connection 122, cylinder 126 retracts at the same time, causing pressure fluid to be exhausted from pressure side 128 of such cylinder and through line 130 to the side of winch motor 112 for taking up line. Exhaust fluid from winch motor 112 then passes through line 119, line 118, and valve 116 to sump 138.

FIG. 4 diagrams in simplified form another hydraulic circuit to illustrate another embodiment wherein single-acting cylinders may be used in tandem to accomplish the same results as the single double-acting boom extension cylinder of FIG. 2. Like FIG. 3, FIG. 4 also includes a first reversible fluid motor means comprising winch motor and a second reversible fluid motor means comprising a single-acting boom extension cylinder 152 and a single-acting cylinder 156. The piston rods of the two cylinders are connected in tandem by a rigid connection 160. The boom extension cylinder and winch motor are supplied with pressure fluid by a pump 162, with the direction of flow being determined by selector valve 164.

Selector valve 164 may be positioned to send pressure fluid through line l66and through line 168 to the pressure side 154 of boom extension cylinder 152 to extend such cylinder and thus the boom. When this occurs, rigid connection 160 causes simultaneous extension of cylinder 156 to discharge fluid from the pressure side 158 of the latter cylinder into line 170, which connects cylinder 156 in series with winch motor 150. Line 170 directs pressure fluid into the side of winch motor 150 that will operate such motor in a direction for paying out line and thus lowering a load. Pressure fluid is discharged from winch motor 150 into line 172, which returns the fluid through line 176 to sump. To retract theboom with the circuit of FIG. 4, selector valve 164 is positioned so that pump 162 supplies fluid through line 176 and line 172 to the side of winch motor 150 for taking in line. Winch motor 150 discharges pressure fluid into line 170, which directs the fluid to the pressure side 158 of cylinder 156, retracting such cylinder. Rigid connection 160 effects simultaneous retraction of the boom extension cylinder 152. When this occurs, fluid is discharged from the pressure side of the boom extension cylinder into line 168 and through valve 164 to sump 178.

Having described a preferred embodiment of the invention as illustrated by FIG. 2 and several alternative embodiments as represented by the circuits of FIGS. 3 and 4, it should be apparent to those skilled in the art that the invention permits of modification in arrangement and detail.

I claim as my invention all such modifications as come within the true spirit and scope of the following claims:

1. In a load-handling apparatus including an extensible boom with line means extending from an extensible portion of said boom and suspending load-handling means therefrom,

fluid pump means,

driven line storage means operable when driven to pay out and retrieve said line means,

said line storage means including fluid winch motor means for driving said line storage means,

fluid boom motor means operably connected to said pump means and operable upon extension of said boom to receive and deliver a flow of pressure fluid,

brake means biased to an engaged position to restrain operation of said line storage means,

said winch motor means being connected in series with said boom motor means at all times during extension of said boom in a manner so that fluid under operating pressure flows through said winch motor means in a direction for paying out said line means whenever said boom extends,

and control means operable to extend said boom and simultaneously release said brake means so that said line means is continuously paid out during any extension of said boom to prevent interference between said load-handling means and said boom,

said control means including:

first boom control valve means in a first fluid circuit connecting said winch motor means and said boom motor means in series with said pump means for controlling the extension and retraction of said boom,

second winch control valve means in a second fluid circuit connecting said winch motor means with said pump means and bypassing said boom motor means for controlling the operation of said winch motor means without operating said boom,

said circuits and first and second valve means providing an interlock means interlocking said first and second valve means in a manner such that said first valve means can function to extend said boom only when said second valve means is in a neutral position blocking flow through said second circuit to said winch motor means to prevent independent operation of said winch as said boom extends.

2. Apparatus according to claim 1 wherein said second control valve means is operable to control the operation of said winch motor means regardless of the position of said first control valve means.

3. Apparatus according to claim 1 wherein movement of said second control valve means to a position for operating said winch motor means blocks flow from said pump means to said first control valve means. 

1. In a load-handling apparatus including an extensible boom with line means extending from an extensible portion of said boom and suspending load-handling means therefrom, fluid pump means, driven line storage means operable when driven to pay out and retrieve said line means, said line storage means including fluid winch motor means for driving said line storage means, fluid boom motor means operably connected to said pump means and operable upon extension of said boom to receive and deliver a flow of pressure fluid, brake means biased to an engaged position to restrain operation of said line storage means, said winch motor means being connected in series with said boom motor means at all times during extension of said boom in a manner so that fluid under operating pressure flows through said winch motor means in a direction for paying out said line means whenever said boom extends, and control means operable to extend said boom and simultaneously release said brake means so that said line means is continuously paid out during any extension of said boom to prevent interference between said load-handling means and said boom, said control means including: first boom control valve means in a first fluid circuit connecting said winch motor means and said boom motor means in series with said pump means for controlling the extension and retraction of said boom, second winch control valve means in a second fluid circuit connecting said winch motor means with said pump means and bypassing said boom motor means for controlling the operation of said winch motor means without operating said boom, said circuits and first and second valve means providing an interlock means interlocking said first and second valve means in a manner such that said first valve means can function to extend said boom only when said second valve means is in a neutral position blocking flow through said second circuit to said winch motor means to prevent independent operation of said winch as said boom extends.
 2. Apparatus according to claim 1 wherein said second control valve means is operable to control the operation of said winch motor means regardless of the position of said first control valve means.
 3. Apparatus according to claim 1 wherein movement of said second control valve means to a position for operating said winch motor means blocks flow from said pump means to said first control valve means. 